highaltitude.log.20111210

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[04:40] <natrium42> o;./
[04:40] <natrium42> err
[04:40] <natrium42> o/
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[07:54] <earthshine> morning
[08:12] Nick change: suga -> sugar
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[09:52] <fsphil> the moon will rise eclipsed tonight in the UK
[09:52] <fsphil> that should look really odd
[09:53] <joph> cloouds here, so no chance to see it ;)
[09:54] <Darkside> should be perfectly viewable here
[09:54] <Darkside> if the clouds go away
[09:55] <fsphil> *looks outside* ah nuts
[09:55] <joph> you can be glad ;)
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[10:38] <nosebleedKT> hi !
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[15:29] <mattltm> Hi all :)
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[16:32] <fsphil> the eclipse has started hasn't it?
[16:33] <NigeyS> yuhuh
[16:34] <fsphil> oh it's already finished
[16:38] <NigeyS> dam, thought it was 5:18 it hit partial not 4:18 :( cloudy anyway, wouldnt have seen it :(
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[17:02] <LazyLeopard> The total phase was pretty much over before moon rise here.
[17:02] <LazyLeopard> My sister in Australia said she had a fine view of it, though.
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[18:06] <Darkside> we had heaps of cloud here
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[20:24] <Lunar_Lander> hello
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[22:04] <chris_99> this may be slightly off topic, noones done anything to do with cloud detection before per chance?
[22:13] <SpeedEvil> Look for 300Hz energy in light from sky.
[22:13] <x-f> White Star team has, iirc
[22:13] <SpeedEvil> Or look for high IR temperatures
[22:14] <chris_99> alas these are just standard photographs
[22:20] <Laurenceb_> can anyone recommend some high temperature ceramics for use with steam?
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[22:20] <SpeedEvil> diamond
[22:20] <Laurenceb_> i was thinking of carbon-carbon but it reacts
[22:20] <Laurenceb_> lol
[22:20] <SpeedEvil> Sapphire
[22:20] <SpeedEvil> What temperature steam?
[22:20] <Laurenceb_> anything better than magnesium dioxide?
[22:20] <Laurenceb_> it has to be machinable
[22:20] <Laurenceb_> 2000C
[22:20] <SpeedEvil> That's quite warm
[22:20] <Laurenceb_> solar furnace
[22:20] <SpeedEvil> At normal pressures?
[22:21] <Laurenceb_> -micro size one
[22:21] <Laurenceb_> at <0.1bar
[22:21] <Laurenceb_> absolute
[22:21] <SpeedEvil> Is this the silly solar-thermal thingy?
[22:21] <Laurenceb_> cubesat yes
[22:21] <SpeedEvil> How do you get that mirror in a cubesat?
[22:22] <Laurenceb_> rofl, good question
[22:22] <Laurenceb_> edmund optics make a parabolic concentrator, but its 100mm diameter
[22:22] <Laurenceb_> it gets in the way of the assembly bolts
[22:22] <Laurenceb_> i was wondering if it could be milled at all - its borofloat glass 5mm think
[22:22] <Laurenceb_> *thick
[22:22] <SpeedEvil> trivial
[22:23] <SpeedEvil> dremel with diamond bit will go through it like butter
[22:23] <Laurenceb_> interesting
[22:23] <SpeedEvil> And if you only need that quality of mirror, you can go _much_ lighter
[22:23] <Laurenceb_> i cant find any
[22:24] <Laurenceb_> needs to be off the shelf if this is to be realistic
[22:25] <Laurenceb_> newport have some electrodeposited nickel ones
[22:25] <SpeedEvil> you don't need a good mirror.
[22:25] <Laurenceb_> but glass is quite light
[22:25] <SpeedEvil> It only needs to reflect to ~0.2 degree accuracy
[22:25] <Laurenceb_> ...only
[22:25] <SpeedEvil> 0.2 degree is a _bad_ (visually) mirror
[22:26] <Laurenceb_> yes, but still hard to make
[22:26] <Laurenceb_> the mirror is actually only ~120grams
[22:26] <SpeedEvil> You're looking for a deep f-ratio, I guess?
[22:26] <Laurenceb_> total mass of the present design in 600 dry
[22:26] <Laurenceb_> yes
[22:27] <Laurenceb_> but yeah itd be nice to get a light mirror
[22:27] <Laurenceb_> lol
[22:30] <SpeedEvil> I wonder if sapphire is actually silly
[22:30] <SpeedEvil> you get a significant boost if you do the refractive index trick.
[22:31] <SpeedEvil> But it would mean a fair bit of nasty machining.
[22:31] <Laurenceb_> low melting point
[22:31] <Laurenceb_> compared to magnesium oxide
[22:32] <SpeedEvil> What size are you hoping for for the hot bit?
[22:33] <SpeedEvil> t^4 is a hideously nasty term when it's 3000 times more than room temp
[22:34] <SpeedEvil> Also - the f-ratio sets the maximum temp, as it sets the amount of 'sky' covered by the 'sun'
[22:34] <Laurenceb_> about 3mm diameter
[22:35] Action: SpeedEvil looks at his '100000 candlepower' torch.
[22:36] <Laurenceb_> heh
[22:36] <Laurenceb_> didnt think of that one
[22:36] <Laurenceb_> http://www.matweb.com/search/datasheettext.aspx?matguid=2d5224eb7f5541de95e132fdf610722d
[22:36] <SpeedEvil> I suspect it will melt somewhat due to the IR
[22:36] <Laurenceb_> says up to 1800C
[22:37] <Laurenceb_> oh - low temperature plastic?
[22:37] <SpeedEvil> yeah
[22:37] <Laurenceb_> polystyrene?
[22:37] <SpeedEvil> Of course, you really want to coat the capsue with a selective coating.
[22:37] <SpeedEvil> probaby acrylic
[22:37] <Laurenceb_> i was thinking soot XD
[22:37] <SpeedEvil> Err - no.
[22:38] <SpeedEvil> I mean selective to reduce re-emission
[22:38] <Laurenceb_> ah
[22:38] <Laurenceb_> i dont think it matters
[22:38] <Laurenceb_> its going to be getting ~11W
[22:38] <SpeedEvil> If you could actually hit 3mm.
[22:38] <Laurenceb_> losing ~3W to the feed pipe
[22:38] <SpeedEvil> Which is gonna be fun.
[22:39] <SpeedEvil> I guess the nozzle cuts out the back of the parabola?
[22:40] <Laurenceb_> and sticking about 100mw into the actual steam
[22:40] <Laurenceb_> the parabola has a 30mm hole in the back
[22:41] <Laurenceb_> http://www.edmundoptics.com/products/displayproduct.cfm?productid=3096
[22:41] <Laurenceb_> second one down
[22:45] <SpeedEvil> platinum?
[22:45] <SpeedEvil> hmm - maybe not, I guess you'd need Ir/Rh
[22:46] <SpeedEvil> And yes' it's $2000/oz - but you'd need _way_ less than an ounce
[22:46] <Laurenceb_> wont it oxidise?
[22:47] <Laurenceb_> steam is crazy corrosive at those temperatures
[22:47] <SpeedEvil> http://gltrs.grc.nasa.gov/reports/1997/TM-107453.pdf
[22:48] <Laurenceb_> hmm water decomposes at 3000C
[22:48] <SpeedEvil> Water simply for convenience?
[22:49] <Laurenceb_> due to regs on what can be carried
[22:49] <SpeedEvil> ah
[22:49] <Laurenceb_> otherwise ammonia is way better
[22:49] <Laurenceb_> and less corrosive
[22:50] <SpeedEvil> Ir/Rh seems ideal - but not practical to make, I guess
[22:50] <BrainDamage> make a rocket, and start harvesting asteroids? >_>
[22:53] <Laurenceb_> i dont see any need for selective coatings
[22:54] <SpeedEvil> If you can hit that 3mm size, maybe not
[22:56] <Laurenceb_> the mirror will do it - just needs the pointing
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[23:00] <SpeedEvil> I make a 3mm diameter sphere at 2000K losing ~24W
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[23:01] <SpeedEvil> It's almost exactly 1W/mm^2
[23:08] <Laurenceb_> would need a proper sim
[23:09] <jcoxon> evening all
[23:10] <SpeedEvil> Laurenceb: Well - not for just working out the black body emission of a 3mm sphere.
[23:10] <Lunar_Lander> hello jcoxon
[23:11] <SpeedEvil> How much worse is the ISP if it drops to say 1500C?
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[23:11] <Laurenceb_> about 30 seconds
[23:11] <Laurenceb_> 200 as opposed to 230
[23:12] <SpeedEvil> Hmm
[23:13] <Laurenceb_> its complex - theres conduction to the feedline and nozzle
[23:14] <SpeedEvil> Indeed.
[23:14] <SpeedEvil> And IR losses from the feedline.
[23:15] <SpeedEvil> I guess you can mitigate those at least with careful reflectors
[23:16] <SpeedEvil> Fun project
[23:16] <SpeedEvil> Of course, that raises other issues.
[23:16] <SpeedEvil> Like - how small can you get a pulsed resistojet.
[23:17] <Laurenceb_> resistojets are poor
[23:17] <Laurenceb_> hard to get as hot
[23:17] <Laurenceb_> also not done before
[23:19] <SpeedEvil> I mean something like a 2W solar array -> lifepo4 -> 200W resistojet
[23:19] <Laurenceb_> machinable magnesium oxide is a pita to buy
[23:19] <Laurenceb_> yeah
[23:19] <Laurenceb_> but its tricky to get very hot
[23:20] <SpeedEvil> SiC?
[23:20] <Laurenceb_> impossible to machine
[23:23] <Laurenceb_> the idea would be to prove the concept - not get the best results
[23:24] <SpeedEvil> hmm
[23:26] <SpeedEvil> Blue LED photon drives should actually be measurable.
[23:26] <SpeedEvil> (but unspeakably silly)
[23:27] <SpeedEvil> Magnetorquers too?
[23:27] <Laurenceb_> yes, two axis
[23:27] <Laurenceb_> for spin stabilisation
[23:30] <Laurenceb_> know anywhere to buy carbon composite panel?
[23:30] <SpeedEvil> you mean ccc?
[23:31] <Laurenceb_> carbon composite with alu core
[23:31] <SpeedEvil> ah
[23:31] <SpeedEvil> I was pondering making Al/C composite
[23:31] <SpeedEvil> It doesn't look _that_ bad
[23:32] <SpeedEvil> you dip the carbon in some flux that I forgot.
[23:32] <SpeedEvil> then - for example - drag the carbon rope through a Al bath and orifice
[23:32] <SpeedEvil> and rapidly cool
[23:32] <Laurenceb_> i thought that didnt work
[23:33] <Laurenceb_> only boron fibre worked
[23:33] <SpeedEvil> You need to cool it fast - on the order of 3s or so
[23:33] <SpeedEvil> Or you get nasty intermetallics that eat the fibre.
[23:33] <Laurenceb_> eww
[23:35] <Laurenceb_> http://dragonplate.com/ecart/categories.asp?cID=76
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[23:36] <SpeedEvil> haha
[23:37] Action: SpeedEvil is ordering _beeeeg_ sheets of 'honeycomb' PP in the next few days.
[23:37] <SpeedEvil> http://www.theplasticshop.co.uk/corrugated-polypropylene-sheet-2951-0.html
[23:38] <Laurenceb_> http://dragonplate.com/ecart/product.asp?pID=4332&cID=110
[23:38] <Laurenceb_> perfect for bulkheads
[23:38] <Laurenceb_> ah that
[23:38] <SpeedEvil> That's not - hideously - expensive
[23:39] <SpeedEvil> More specs'd be nice.
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[23:45] <jcoxon> anyone around to help with some datasheet decoding?
[23:46] <SpeedEvil> ?>
[23:46] <Randomskk> I love how opaque datasheets can be, what're you trying to work out?
[23:46] <jcoxon> i actually think its my own inability to work it out
[23:47] <jcoxon> http://www.u-blox.com/en/download/documents-a-resources/u-blox-6-gps-modules-resources.html
[23:47] <jcoxon> the receiver description
[23:47] <jcoxon> basically i'm trying to work out hte command to put the ublox in cylical power saving mode
[23:48] <Laurenceb_> http://starshipmodeler.biz/shop/index.cfm/product/1996_133/micro-brass-tube---03mm-diameter.cfm
[23:48] <Laurenceb_> nice
[23:48] <Randomskk> have you tried just hooking it up to u-center and setting the power saving mode and looking at the command it sent? it has a window that shows all the over the wire stuff
[23:49] <jcoxon> thats probably best
[23:52] <jcoxon> sadly my wine has bust
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[00:00] --- Sun Dec 11 2011